# ifndef CPPAD_LOCAL_PLAY_SUBGRAPH_ITERATOR_HPP
# define CPPAD_LOCAL_PLAY_SUBGRAPH_ITERATOR_HPP
// SPDX-License-Identifier: EPL-2.0 OR GPL-2.0-or-later
// SPDX-FileCopyrightText: Bradley M. Bell <bradbell@seanet.com>
// SPDX-FileContributor: 2003-25 Bradley M. Bell
// ----------------------------------------------------------------------------

# include <cppad/local/play/random_iterator.hpp>

// BEGIN_CPPAD_LOCAL_PLAY_NAMESPACE
namespace CppAD { namespace local { namespace play {

/*!
\file random_iterator.hpp
*/

/*!
Constant subgraph iterator for a player object.

\tparam Addr
An integer type capable of representing the largest value in the vectors
var_arg, op2arg_index, op2var_index, var2op_index.

Except for constructor, the public API for this class is the same as
for the sequential iterator class.
*/
template <class Addr>
class const_subgraph_iterator {
private:
   /// a random iterator used to access player information
   const const_random_iterator<Addr>* random_itr_;

   /// sorted subset of operator indices that we will include
   const pod_vector<addr_t>* subgraph_;

   /// index in subgraph of current operator
   /// The initial value for this index must be zero or subgraph.size()-1.
   size_t subgraph_index_;

public:
   /// default constructor
   const_subgraph_iterator(void) :
   random_itr_(nullptr) ,
   subgraph_(nullptr)   ,
   subgraph_index_(0)
   { }
   /// default assignment operator
   void operator=(const const_subgraph_iterator& rhs)
   {
      random_itr_      = rhs.random_itr_;
      subgraph_        = rhs.subgraph_;
      subgraph_index_  = rhs.subgraph_index_;
      return;
   }
   /*!
   Create a subgraph iterator starting either at beginning or end of subgraph
   */
   const_subgraph_iterator(
      const const_random_iterator<Addr>&    random_itr , ///< random_itr_
      const pod_vector<addr_t>*             subgraph   , ///< subgraph_
      size_t subgraph_index                            ) ///< subgraph_index_
   :
   random_itr_      ( &random_itr )       ,
   subgraph_        ( subgraph )          ,
   subgraph_index_  ( subgraph_index )
   {  CPPAD_ASSERT_UNKNOWN(
         subgraph_index == 0 || subgraph_index == subgraph->size() - 1
      );
   }
   /*!
   Advance iterator to next operator
   */
   const_subgraph_iterator<Addr>& operator++(void)
   {  ++subgraph_index_;
      return *this;
   }
   /// No correction necessary when using random access to player
   void correct_before_increment(void)
   {  return; }
   /*!
   Backup iterator to previous operator
   */
   const_subgraph_iterator<Addr>& operator--(void)
   {  --subgraph_index_;
      return *this;
   }
   /*!
   No correction necessary when using random access to player.

   \param op_arg
   not used or modified.
   */
   void correct_after_decrement(const addr_t*& op_arg)
   {  return; }
   /*!
   \brief
   Get information corresponding to current operator.

   \param op [out]
   op code for this operator.

   \param op_arg [out]
   pointer to the first arguement to this operator.

   \param var_index [out]
   index of the last variable (primary variable) for this operator.
   If there is no primary variable for this operator, var_index
   is not sepcified and could have any value.
   */
   void op_info(
      op_code_var&   op         ,
      const addr_t*& op_arg     ,
      size_t&        var_index  ) const
   {  // op
      size_t op_index = size_t( (*subgraph_)[subgraph_index_] );
      random_itr_->op_info(op_index, op, op_arg, var_index);
   }
   /// current operator index
   size_t op_index(void)
   {  return size_t( (*subgraph_)[subgraph_index_] ); }
};

} } } // BEGIN_CPPAD_LOCAL_PLAY_NAMESPACE

# endif
